lec 3 Flashcards
cell shapes of prokaryotes
1) coccus: basically a sphere
2) rods
3) spirillium: twisted rods
4) spirochete: very good at swimming through liquid and drill into tissues
5) stalk: more complex, their membranes are capable of elongating and creating motile daughter cells. mostly water bond and capable of attaching to water molecules
6) filamentous: forms a very long filaments and the cells that does detach from each other
functions of the cell wall of bacteria
- allows the bacteria to withstand the intracellular osmotic pressure
- shape and rigidity
- on top of the cytoplasmic membrane
gram stain
a procedure to stain cells in order to view them under the microscope
cells are divided into gram stains based on their:
cell wall composition
how to make a gram stain
1) prepare a thin later of bacteria o na slide
2) mix with crystal violet for 1 min –> purple
3) add iodine for 1 min –> purple
4) decolonize with alcohol for 20 sec –> gram +: purple, gram - : color less
5) counterstain with safranin fro 1-2 min –> gram +: purple, gram -: pink to red
gram positive vs gram negative
gram negative has an outer membrane on top of the peptidoglycan
structure of peptidoglycan
- the backbone is basically similar among most
- 2 sugars: N-acetylglucosamine and N-acetylmuramic acid
- side chain attached to the sugars: peptide chain –> D amino acids
- mammals destroys these bacteria by producing lysozyme and breaking the beta 1-4 linkages
gram — is more sensitive to lysozyme, why?
positive, its peptidoglycan is exposed
transpeptidation
polymerization of the sugar backbones that provides rigidity in only one direction
transpeptidation in gram neg
direct cross linkage (covalently)
transpeptidation in gram positive
inter bridge cross linkage, by adding more AAs between the 2 sugars, so then you make it thicker
how does penicillin destroy bacterial infections
inhibits binding the 2 peptide chains together by inhibition transpeptidase enzymes
upto —- % of the cell wall is peptidoglycan
90
proteins attached to the peptidoglycan layer:
1) teichoic acid. *variable can be either or
2) lipoteichoic acid
how does TA and LTA impact the overall charge of the cell
net negative, because they are negative
what happen if LTA is bound to the peptidoglycan
- it binds deeper with it and ends with a glycerol phospholipid
- anchored inside the cytoplasmic memebtan
- makes peptidoglycan fully attached to the cytoplasmic membrane
how are proteins attached to the peptidoglycan layer
enzyme: sortase
(T/F) eukaryotes doen have sortase
true
structure of the outer membrane of gram neg
- porins
- outer membrane proteins
- inside layer: phospholipids
- outer layer: LPS + phospholipids
periplasm space:
it is covered by:
where the peptidoglycan is located
- outer membrane and cytoplasmic membrane
function of LPS
protects the bacteria against antibiotics and host defence system
structure of LPS
a family of complex sugar polymers attached to lipid A
- lipid A contains 6 lipid tails embedded in the membrane
- KDO links lipid A to the polysaccharide chain:
- connected to core polysaccharides (don’t change much)
- and O specific polysaccharides or O antigens:repeating sequences of 2-4 monosaccharides (very variable)
consequences of lipid A
septic shock
pseudomuerin in archaea vs. peptidoglycan
- lack D AAs, instead has L AAs
contains N-acetylalsaminuronic aid instead of NAM - linkage is insensitive to lysozyme, due to its beta 1–> 3 linkage
the great majority of archaea have — and/ or —- on their cell walls. some can be composed of —-
protein, glycoproteins, heteropolyasachchrides
S layer
the cyrtslaline appearance of the cell walls of archaea
it may also be found in bacteria
gram + : on top of the peptidoglycan
gram -: on top of the outer membrane
- esp when the archaea is composed of any of: protein, glycoprotein, sugar
the capsule or slime layer are composed of — for majority and —- in some gram positive
heteropolyasachcrides
homopolysaccharides
how is the capsule attached to the cell
it is covalently bound to either the outer membrane or the peptidoglycan layer
fxn of capsule
doesn’t confer sig strength
- due to its glue like texture, external matter stick to it therefore, protection against the host defence system
flagella and fimbriae are —- than the size of the bacteria
larger
function of fimbriae
used for attachments and anchor the cell to something. these are short filaments o the surface of the bacteria
monotrichous vs. peritirichous vs. lophotrichous
diagrams
structure of flagella
diagrams
fimbriae is found primarily on gram — bacteria
negative
movement in peritrichous
forward + change direction
movement in mono and lopho
forward and reverse
how is fimbriae attached to gram positive
via sortase on the peptidoglycan
assembly of fimbriae for both gram neg and pos
diagram
taxis
directed movement toward or away from a gradient of chemical or physical agents
- when there is an attractant, the bacteria keeps moving in the right direction. so it spends more time in the direction that is favoured
name the surface appendages of bacteria and archaea
flagella, fimbriae
what is an endospore
highly differentiated cells that are extremely resistant to harsh environments
- safety vessel for the genome of a species
2 bacterias that are well known for producing endospore
clostridium, bacillus
structure of and endospore (outer most layer to the inner most)
1) exosporium
2) spore coat
3) core wall
4) cortex
5) DNA
exosporium
a coat of protein on top of the spore
spore coat
layers of protein that are only found in the spores of the species (spore specific protein)
core wall
contains some protein and genome of the species of interest
cortex
on top of the core wall, thick layer of peptidoglycan
in the core of an endospore, besides the genome and proteins you also have:
1) SASPS
2) Dipicolnic acid (DPA) + Ca2+
SASPS
bind to the DNA an =d protect it from bad things ,esp UV light
DPA + Ca2+
they dehydrate the core in order to stop enzymatic activity therefore, keep the spore fresh
vegetative cycle
where the bacteria is actively growing and dividing
sporulation
when the env becomes harsh a spore is formed
during germination —– is increased, resulting in —-
water uptake, outgrowth
cell inclusions
in bacteria and archaea, nrg reserves and building blocks are sometimes stored in granules or inclusions
cell inclusions are often enclosed by
a single layer of phospholipid, protein, glycoprotein
what nutrients are stored in cell inclusions
P,S,C
How are some bacteria able to respond to earth’s magnetic field
their cell inclusions store magnetites, and allows the cells to respond to magnetic fields
- meganotaxis
how do cell inclusions confer buoyancy
when they store gas, the cell can float on the water and be closer to areas with a higher level of O2
